In general, an increasing number of tires of a radial structure have been produced to meet needs from users in the field of large-sized tires for construction vehicles which are termed as OR tires (Off-the-Road Tires). A method of producing such a radial tire is usually performed with the following procedure. To begin with, a first green tire which has only a tire carcass including a carcass ply and a bead core is formed by use of a first step molding machine. By use of a second step molding machine, subsequently, the first green tire is inflated to have an external diameter of a predetermined size, and belts and tread rubber are wound around the outer periphery of the first green tire thus inflated. Thereby, the first green tire is formed into a completed green tire. Thereafter, the completed green tire is cured by use of a curing machine.
Heretofore, Japanese patent application Kokai publication No. Sho.49-15776 has proposed a measure for improving a method of producing a pneumatic radial tire, according to which a single bladder is used dually as an inflating bladder of the second step molding machine and as an inflating bladder of the curing machine, thereby simplifying the production facilities. However, what costs most in the facilities for producing radial tires is the first step molding machine and the second step molding machine. According to the aforementioned measure for improving the method of producing a pneumatic radical tire, the first step molding machine and the second step molding machine are still the required facilities. For this reason, the aforementioned measure still needs not only large costs for these machines but also a large space where the machines are installed. As a consequence, the proposed measure has not been a fundamental measure for improving the method of producing a pneumatic radial tire.